﻿using System;
using System.Diagnostics;
using System.Linq;
using System.Runtime.InteropServices;

namespace Alvin.Form.Utils
{
    public static class SoftSingleUtil
    {
        ///<summary>
        /// 该函数设置由不同线程产生的窗口的显示状态
        /// </summary>
        /// <param name="hWnd">窗口句柄</param>
        /// <param name="cmdShow">指定窗口如何显示。查看允许值列表，请查阅ShowWlndow函数的说明部分</param>
        /// <returns>如果函数原来可见，返回值为非零；如果函数原来被隐藏，返回值为零</returns>
        [DllImport("User32.dll")]
        private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow);
        /// <summary>
        ///  该函数将创建指定窗口的线程设置到前台，并且激活该窗口。键盘输入转向该窗口，并为用户改各种可视的记号。
        ///  系统给创建前台窗口的线程分配的权限稍高于其他线程。
        /// </summary>
        /// <param name="hWnd">将被激活并被调入前台的窗口句柄</param>
        /// <returns>如果窗口设入了前台，返回值为非零；如果窗口未被设入前台，返回值为零</returns>
        [DllImport("User32.dll")]
        private static extern bool SetForegroundWindow(IntPtr hWnd);
        private const int SwShownomal = 1;

        private static void HandleRunningInstance(Process instance)
        {
            ShowWindowAsync(instance.MainWindowHandle, SwShownomal);//显示
            SetForegroundWindow(instance.MainWindowHandle);//当到最前端
        }

        private static Process RuningInstance()
        {
            var currentProcess = Process.GetCurrentProcess();
            var processes = Process.GetProcessesByName(currentProcess.ProcessName);
            return processes.FirstOrDefault(process => process.Id != currentProcess.Id);
        }
        /// <summary>
        /// Winform程序以单例运行
        /// </summary>
        public static void Single<T>() where T : System.Windows.Forms.Form, new()
        {
            var process = RuningInstance();
            if (process == null)
            {
                var mainForm = new T();
                System.Windows.Forms.Application.Run(mainForm);
            }
            else
            {
                HandleRunningInstance(process);
            }
        }
    }
}
